JPS62202009A - Continuous and preliminary treatment of molten iron - Google Patents

Abstract

PURPOSE:To enable effective preliminary refining of a molten iron while decreasing the erosion of a blast furnace spout by blowing refining agents into the molten iron from plural nozzles which are arranged in the flow direction of the molten iron and disposed to direct the top ends thereof toward the center from the wall surface sides of the spout at the time of allowing the molten iron tapped from the blast furnace to flow in the blast furnace spout. CONSTITUTION:Plural pieces of the nozzles for blowing the refining agents are mounted between a skimmer 2 and slag discharge port 1a of the blast furnace spout 1 in order to make preliminary refining such as desiliconizing, dephosphorizing and desulfurizing at the time of allowing the molten iron 3 tapped from the blast furnace to flow in the blast furnace in an arrow direction. The nozzles 4 are disposed by arraying the same in two rows in the flow direction (arrow) of the molten iron 3. The nozzles 4 are so disposed as to direct the top ends thereof toward the central part from the wall surface sides of the blast furnace spout 1. The angles of inclination thereof are set at alpha=15 deg. and theta=10 deg. and the nozzles 4 are disposed zigzag. The molten iron 3 is thoroughly stirred by only the blowing of the refining agents. Formed molten slag 6 parts from the wall surfaces of the spout 1 and gathers at the center, then the slag is discharged from the slag discharge port 1a and therefore, the erosion of the inside wall surfaces (particularly the part of the molten slag 6) of the spout 1 by the molten slag 6 is obviated and the service life of the spout 1 is extended.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a hot metal pretreatment method for pre-refining by adding a refining material to hot metal flowing in a blast furnace gutter.

[Conventional technology]

In recent years, as the requirements for steel components have become stricter (lower p, s, steelization), the necessity and importance of hot metal pretreatment has increased.
Furthermore, due to the advantages of omitting steps and simplifying treatment, hot metal pretreatment by adding a refining agent in the blast furnace trough has become popular. Methods for adding refining agents into hot metal can be broadly divided into overlay methods, injection methods, and blasting methods. Among these methods, the injection method using an immersion lance is the most superior in terms of addition and mixing of the refining agent. However, considering the running cost due to lance erosion, recently the
As seen in Japanese Patent No. 8-130208, the blasting method in which a refining agent is injected into the top of the hot metal using a high-speed flow has come to be widely adopted.

However, this preliminary processing has caused a problem that did not exist in the past. In other words, in the conventional steelmaking method that does not perform pretreatment, the slag flowing in the blast furnace gutter contains SiO2 and Ca.
Since it contains substances such as O as its main component, it acts extremely stably on gutter refractories, extending the lifespan of 1-proof refractories. However, when pre-treatment of hot metal began to be carried out, components that were harmful to refractories, mainly FeO, were mixed into the produced slag, and corrosion caused by this became a problem. Erosion of the gutter refractory is most severe at the point where the boundary between the hot metal and the slab meets, and since the surface of the hot metal changes only slightly due to the flow rate of the hot metal and is almost constant (in the range of about 20 to 30 degrees), the life of the gutter can be further extended. They put a mortar on it to make it short-lived.

Conventionally, as a solution to this problem, proposals have been made to change the material of the large bite-resistant material to a different material, or to blow protective gas from the side wall of the gutter to direct the slag to the center of the gutter, as shown in Japanese Patent Application Laid-Open No. 57-134505. are doing.

[Problems that the invention seeks to solve] However, in the former case, it is necessary to select the material according to the content of the hot metal pretreatment, and the selection is difficult, and the material must be changed every time the content of the pretreatment changes. This is difficult from an operational standpoint as well. Also, it will involve higher quality materials, so
There is also the problem that the refractory unit cost (refractory cost per amount of hot metal processed) worsens.

In the latter case, there is a practical problem because the protective gas lowers the temperature of the hot metal and it is difficult to work when constructing the gutter.

Therefore, as a result of various studies conducted by the present inventor, the blasting method has disadvantages in that there are many ripples on the surface of the hot metal and severe erosion of the refractory. We have discovered that this can be solved by applying a large force to the slag and adjusting the blowing direction, and hereby provide a method for continuous pretreatment of hot metal with improved corrosion resistance.

[Means for solving problems]

As a result of intensive research, the present invention has been developed in a continuous hot metal pretreatment method in which a refining agent is added to a gutter that continuously flows hot metal. The refining agent is disposed closer to the center, and the refining agent is blown into the hot metal at high speed from the top surface of the hot metal through the plurality of nozzles.

The plurality of nozzles are Sdera 74. ' In order to reduce knee and give force to the slag layer in the center of the gutter, Oo < α along the hot metal flow direction as shown in Figures 2 and 3.
An angle of <45°, particularly 5° and α<30° is preferable, and it is also desirable to incline at an angle of Oo<θ and 45° along the cross-sectional direction of the hot metal. It is best to adjust the blowing angles α and θ so that the floating point of the blown refining agent is at the center of the gutter by taking into account the flow rate of the hot metal. It becomes difficult to penetrate into the hot metal, resulting in an increase in splashy and a significant decrease in refining reaction efficiency. Furthermore, the effect is even greater by arranging the nozzles in a staggered manner.

As the carrier gas for the refining material, in addition to an inert companion gas such as N2, compressed air or a bridge gas such as oxygen can be used. The blowing pressure of the carrier gas is not determined depending on the depth of the hot metal or the nozzle diameter, but it is approximately 1.5 to 6 kgf/ctA in order to give the slag layer a force to move toward the center of the gutter and to ensure sufficient stirring. It is desirable to do so.

[Effect]

By blowing the refining material, a force is generated in the slag layer toward the center of the gutter, and the slag layer leaves the gutter wall surface and gathers in the center and flows, reducing erosion of the gutter refractories.

〔Example〕

Examples will be described below with reference to the drawings.

FIG. 1 is a schematic diagram of an apparatus used for carrying out the present invention, and in the figure, 1 is a blast furnace gutter constructed of refractory material. For refractories, At205: 80 wt%, 5iC-4-C: 15
wt% monolithic refractories and other refractories can be used.

A skinmer 2 is arranged on the upstream side of the blast furnace gutter 1, and a slag discharge port 1a is provided on the gutter wall surface on the downstream side of the skinmer 2. Between the skinmer 2 and the slag discharge port 1a, a plurality of nozzles 4 are arranged on the surface of the hot metal 3 for spraying a refining agent onto the surface of the hot metal 3 for preliminary refining. The plurality of nozzles 4 are arranged in two rows in the hot metal flow direction (arrow), and the tips of the nozzles 4 are oriented toward the center of the gutter 1 from the wall side. Specifically, nozzle 4.
The inclination angles of the nozzles 4 are set to α=15° and θ=10°, and the nozzles 4 are arranged in a staggered manner. In addition, 5 is a tongue into which a refining agent is put.

Using such equipment, hot metal 10 Ton/min
For this purpose, dephosphorization was performed. Refining agent is CaO: 4.0 w
i%, CaF: 8 wt%, mill scale: 50
wt%. This refining agent was blown into the reactor at a pressure of 400 kg/M using a carrier gas.

Sufficient stirring was achieved by this blowing, and the slag 6 moved away from the wall surface of the gutter 1 and proceeded toward the center, and was discharged from the slag discharge port 1a.

In order to compare the effects, gutter refining was carried out under the same conditions and the amount of erosion at the position where the refractory was in contact with the hot metal surface was measured, and the results were obtained as shown in Table 1 below.

Table 1 The amount of erosion shown in this table is after 2 hours, no treatment means no preliminary refining, and the conventional method is when a plurality of nozzles are simply arranged in the hot metal flow direction. The refractory contains At, O,: 80 wt%, SiC+C:
A 15 wt monolithic refractory was used.

As a result, the present invention was found to be superior to the conventional method and comparable to no treatment.

〔Effect of the invention〕

As explained above, the present invention has the following effects.

■ Gutter life can be extended.

■ There is little interference with the next stage of blasting, resulting in high refining efficiency.

■ Since it can be injected from close to the wall, it can stir the entire cross section of the hot metal flow.

■ The slag layer is thick in the center and thin near the wall, so there is less scattering of the refining agent by the slag layer during injection.

■ Splash can be significantly reduced by adjusting the nozzle angle.

■ Wall protection gas is not required.

These effects become noticeable when applied to dephosphorization treatment that causes severe corrosion of refractories.

[Brief explanation of drawings]

Fig. 1 is a perspective view schematically showing the device used in the present invention, Fig. 2 is a front view of the nozzles arranged along the flow direction of hot metal, and Fig. 3 is a perspective view of the nozzles arranged along the hot metal flow direction. It is a side view of a nozzle. DESCRIPTION OF SYMBOLS 1... Blast furnace gutter, 1a... Slag discharge port, 2... Skimmer, 3... Hot metal, 4... Nozzle, 5... Tank, 6... Slag. Figure 2 Figure 3

Claims (1)

[Claims] (1) In a hot metal continuous pretreatment method in which a refining agent is added to a gutter that continuously flows hot metal, multiple nozzles are arranged in the hot metal flow direction and the tip of each nozzle is directed from the gutter wall side toward the center. A continuous preliminary treatment method for hot metal, characterized in that a refining agent is blown into the hot metal from the upper surface of the hot metal at high speed through a plurality of nozzles.